Higher-order multipole amplitudes in charmonium radiative transitions
Higher-order multipole amplitudes in charmonium radiative transitions
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DOI：
10.1103/physrevd.80.112003
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发表时间：
2009-10
影响因子：
5
通讯作者：
M. Artuso;E. al.
中科院分区：
文献类型：
--
作者：
M. Artuso;E. al.
利用CLEO-c中的24x10{sup 6}{psi}{sup‘}{等同_to}{psi}(2S)衰变，我们在木炭的电偶极主导的辐射跃迁中寻找了更高的多极混合物。我们发现，我们的数据与理论预测的磁四极(M2)振幅在跃迁{psi}{sup‘}{殖利率}{伽马}{chi}{subc1，c2}和{chi}{subc1，c2}{殖利率}{伽马}J/{psi}中有很好的一致性，这与以前的一些测量结果形成了鲜明的对比。设b{sub2}{sup J}和a{sub2}{sup J}表示上述各个衰变中的归一化M2振幅，其中上标J表示{chi}{subCJ}的角动量。通过对全五参数角分布进行无宾极大似然拟合，我们得到了J{Sub{chi}}=1的M2混合体的下列值：a{sub2}{sup J={sup 1}}=(-6.26{+-}0.63{+-}0.24)x10{sup-2}和b{sub2}{sup J={sup 1}}=(2.76{+-}0.73{+-0.23)x10{sup-2}，这与魅力夸克的反常磁矩消失的理论预期相符。对于J{sub{chi}}=2，如果我们像理论预测的那样将电八极(E3)的振幅固定为零，则得到a{sub2}{sup J={sup 2}}=(-9.3{+-}1.6{+-0.3)x10{sup-2}}和b{sub2}{sup J={sup 2}}=(1.0{+-]1.3{+-0.3)x10{sup-2}。如果我们考虑E3幅度，通过四个参数的拟合，我们发现a{sub2}{sup J={sup 2}}=(-7.9{+-}1.9{+-}0.3)x10{sup-2}，b{sub2}{sup J={sup 2}}=(0.2{+-}1.4{+-}0.4)x10{sup-2}，A{sub3}{sup J={sup 2}}=(1.7{+-}1.4{+-}0.3)x10{sup-2}，以及b{sub3}{supmore»J={sup 2}}=(-0.8{+-}1.2{+-}0.2)x10{sup-2}。我们确定比率a{sub2}{sup J={sup 1}}/a{sub2}{sup J={sup 2}}=0.67{sub0.13}{sup+0.19}和a{sub2}{sup J={sup 1}}/b{sub2}{sup J={sup 1}}=-2.27{sub0.99}{sup+0.57}，其中理论预测与迷人的夸克磁矩无关，并且是a{sub2}{sup J={sup 1}}/a{sub2}{sup J={sup 2}}=0.676{+-}0.071和a{sub2}{sup J={sup 1}}/b{sup J={sup 1}}=-2.27{+-}0.16。
Using 24x10{sup 6} {psi}{sup '}{identical_to}{psi}(2S) decays in CLEO-c, we have searched for higher multipole admixtures in electric-dipole-dominated radiative transitions in charmonia. We find good agreement between our data and theoretical predictions for magnetic quadrupole (M2) amplitudes in the transitions {psi}{sup '}{yields}{gamma}{chi}{sub c1,c2} and {chi}{sub c1,c2}{yields}{gamma}J/{psi}, in striking contrast to some previous measurements. Let b{sub 2}{sup J} and a{sub 2}{sup J} denote the normalized M2 amplitudes in the respective aforementioned decays, where the superscript J refers to the angular momentum of the {chi}{sub cJ}. By performing unbinned maximum likelihood fits to full five-parameter angular distributions, we found the following values of M2 admixtures for J{sub {chi}}=1: a{sub 2}{sup J={sup 1}}=(-6.26{+-}0.63{+-}0.24)x10{sup -2} and b{sub 2}{sup J={sup 1}}=(2.76{+-}0.73{+-}0.23)x10{sup -2}, which agree well with theoretical expectations for a vanishing anomalous magnetic moment of the charm quark. For J{sub {chi}}=2, if we fix the electric octupole (E3) amplitudes to zero as theory predicts for transitions between charmonium S states and P states, we find a{sub 2}{sup J={sup 2}}=(-9.3{+-}1.6{+-}0.3)x10{sup -2} and b{sub 2}{sup J={sup 2}}=(1.0{+-}1.3{+-}0.3)x10{sup -2}. If we allow for E3 amplitudes we find, with a four-parameter fit, a{sub 2}{sup J={sup 2}}=(-7.9{+-}1.9{+-}0.3)x10{sup -2}, b{sub 2}{sup J={sup 2}}=(0.2{+-}1.4{+-}0.4)x10{sup -2}, a{sub 3}{sup J={sup 2}}=(1.7{+-}1.4{+-}0.3)x10{sup -2}, and b{sub 3}{supmore » J={sup 2}}=(-0.8{+-}1.2{+-}0.2)x10{sup -2}. We determine the ratios a{sub 2}{sup J={sup 1}}/a{sub 2}{sup J={sup 2}}=0.67{sub -0.13}{sup +0.19} and a{sub 2}{sup J={sup 1}}/b{sub 2}{sup J={sup 1}}=-2.27{sub -0.99}{sup +0.57}, where the theoretical predictions are independent of the charmed quark magnetic moment and are a{sub 2}{sup J={sup 1}}/a{sub 2}{sup J={sup 2}}=0.676{+-}0.071 and a{sub 2}{sup J={sup 1}}/b{sub 2}{sup J={sup 1}}=-2.27{+-}0.16.« less